1. Technical Field
The present invention relates to serial digital interface (SDI) signals. More particularly, this invention it relates to a method and apparatus for indicating the input cable length for SDI signals.
2. Description of Related Art
The length of a cable plays a critical role in the transmission of signals carried thereby. The length of input cable can affect the signals being transmitted both in terms signal degradation and/or a burst of Cyclic Redundancy Check (CRC) errors. For cables that carry Serial Digital Interface (SDI) signals, the cable length becomes especially important because of the so-called cliff effect, which occurs when the cable losses associated with the SDI signal prevent the ability to receive the signals accurately. Thus, knowledge of the cable length becomes important to make sure the cable conforms to a minimum operating threshold.
One technique for measuring the length of a cable link in a computer network involves sending test signals through a cable and examining the characteristics of the received signal. (See for example, U.S. Pat. No. 6,614,236). For purposes of fiber optic cables, the length determination enables a determination of a tolerable propagation delay between a repeater and a base station (See for example, U.S. Publication No. 2004/0233874).
A need exists for a simple reliable technique for determining the length of a cable to carry SDI signals.